WO2024172684A1

WO2024172684A1 - Intelligent solar cell-based power supply device

Info

Publication number: WO2024172684A1
Application number: PCT/RU2023/000043
Authority: WO
Inventors: Дмитрий Николаевич КУШНЕРЁВ; Ирина Александровна КУШНЕРЁВА
Original assignee: Общество с ограниченной ответственностью "СОЛНЕЧНЫЙ МИР"
Priority date: 2023-02-16
Filing date: 2023-02-21
Publication date: 2024-08-22

Abstract

The utility model relates to conversion technology, and can be used for efficiently extracting power from solar panels and converting and transmitting the energy obtained to a commercial network and to a consumer load. A solar cell-based power supply device consists of the following interconnected components: a unit of solar panels, a unit of current and voltage sensors for the unit of solar panels, a DC/DC voltage converter, a DC bus, an inverter, a unit of converter output current and voltage sensors, a DC/DC voltage converter control unit, an inverter control unit, a microcontroller for control and switching, a unit of DC bus current and voltage sensors, an LC filter and an RFI filter, and a unit of load current and voltage sensors, wherein the device further includes a voltage pulse unit mounted between a solar panel and the DC/DC voltage converter. The technical result of the proposed device is an increase in the energy obtained from the unit of solar panels.

Description

INTELLIGENT POWER SUPPLY DEVICE

THE BASIS OF SOLAR BATTERIES

The field of technology to which the solution relates

The solution relates to conversion technology and can be used for efficient power extraction from solar panels, conversion and transmission of the received energy to the industrial network and consumer load, it is also possible to charge batteries and supercapacitors with energy received from the network with further conversion, if necessary, into alternating voltage of industrial frequency to provide the consumer load with guaranteed uninterruptible power supply.

State of the art

A solar-powered device is known, comprising a solar module, a first DC-DC converter, a battery, a second DC-DC converter, a controller and a load. (Patent of the Russian Federation for invention No. 2503120 "Solar-powered device", IPC H02M 3/156, 12/27/2013).

The disadvantages of this device are:

1. Tracking the maximum power point under uniform illumination using one of the classical methods;

2. Lack of connection to the industrial network to ensure battery charging in bad weather conditions, lack of ability to supply energy to the network.

A power plant is known that contains solar cell batteries, energy storage devices, a DC/DC voltage converter, a DC/AC voltage converter, and circuit breakers (Patent of the Russian Federation Invention No. 2397593 “Power plant and method for its control”, IPC H02J 7/35, H01L 31/00, 20.08.2010).

The disadvantages of this device are:

1. The inability to transfer energy obtained from solar panels to the industrial network;

2. Tracking the maximum power point under uniform illumination using one of the classical methods.

A device and method for tracking the maximum power point for an inverter using solar panels are known, consisting of solar panels, an inverter, a system controller and a load. (Patent US 7158395 B2 "Method and apparatus for tracking maximum power point for inverters, for example, in photovoltaic applications", IPC H02M 7/44, 02.01.2007).

The disadvantages of this device are:

1. Tracking the classic maximum on the I-V characteristic of a block of panels and its drift with changes in temperature and uniform changes in illumination, as a result - inefficient power extraction from a block of solar panels;

2. It is not possible to use this device as a backup power source in the event of a power failure.

Also known is a power conversion system with maximum power point tracking, consisting of a maximum power point tracking unit (MPPT), a DC bus, a power converter, and a converter controller. (Patent US 20130027997 A1 "Maximum power point tracking for power conversion system and method thereof", IPC H02M 7/44, 31.01.2013).

The disadvantages of this device are:

1. Tracking the classic maximum on the VAC of a block of panels and its drift with temperature changes and uniform changes illumination, resulting in a shortage of power from the solar panel unit;

2. The absence of an energy storage device (battery or supercapacitor), and, consequently, the impossibility of powering the load with this system in the event of a power failure or low energy production by solar panels.

The closest in technical essence to the claimed solution is a guaranteed power supply device based on renewable energy sources (RU207387U1, 10/26/2021). This patent tracks all zones on the I-V characteristic in case partial shading occurs and a power peak appears "on the left" on the I-V characteristic. When this point is found, energy is taken from the SP using the classical method. For example, there is a step-up converter that takes current from the panel so that the product of current and voltage from the panel has a maximum value. This is an analogue of a rheostat, when the position of the handle (resistance) of the rheostat is selected at which the maximum energy comes from the SP.

The disadvantage of this device is the tracking of several local zones on the VAC of the panel block and its drift with changes in temperature and changes in illumination, as well as tracking the appearance of the point of maximum power during partial shading and power extraction at this point using the classical method, as a result - inefficient power extraction from the solar panel block.

Solution Disclosure

The technical problem of the declared solution is to increase the efficiency of the device consisting of a block of solar panels (SP) and a converter, tracking the true point of maximum power under real operating conditions; transmitting the received energy to the network and load, as well as the charge of the energy storage device from the solar panel unit and from the grid. As a result, the efficiency (efficiency) of power take-off from the solar panel unit increases, and the reliability of power supply to the consumer of electricity increases.

The technical result achieved by using the proposed device is an increase in the energy received from the solar panel unit.

Increasing the flexibility and functionality of the consumer's energy system built on this converter.

Also, an additional increase in the reliability of the guaranteed power supply of the consumer is ensured, which occurs, among other things, due to the use of energy storage devices that receive energy from solar panels and the grid according to a given algorithm, and in the event of a loss of grid voltage, a decrease in the energy received from the solar panels, they ensure uninterruptible power supply to the consumer, due to mixing energy from the storage device with the energy received from the solar panels on the common DC bus, with subsequent conversion to alternating voltage and power supply to the consumer's load.

The technical problem is solved and the technical result is achieved due to the fact that the power supply device based on solar batteries consists of a solar panel unit, a solar panel unit current and voltage sensor unit, a DC/DC voltage converter, a DC bus, an inverter, a unit of current and voltage sensors at the converter output, a DC/DC voltage converter control unit, an inverter control unit, a control and switching microcontroller, a unit of DC bus current and voltage sensors, an LC filter and a radio interference filter, a unit of current and voltage sensors on the load, and a voltage pulse unit installed between the solar panel and the DC/DC voltage converter is additionally introduced into the device. In addition, the DC/DC voltage converter control unit is designed with an additional function for controlling the voltage pulse unit.

Brief description of the drawings

Fig.1 - Structural diagram of the power supply device;

Fig.2 - Family of volt-ampere characteristics of a solar panel depending on temperature and changes in uniform illumination of the panel;

Fig.3 - The essence of the perturbation and observation method when tracking the maximum power point;

Fig.4 - Simplified diagram of the solar panel operation;

Fig.5 - One of the possible implementation options;

Fig.6 - Diagram of possible serial (a) and parallel (b) connection of solar panels.

Implementation of the solution

An intelligent power supply device based on solar batteries consists of a solar panel unit, a voltage pulse unit, a solar panel unit current and voltage sensor unit, a DC/DC voltage converter, a DC bus, a DC bus current and voltage sensor unit, a reversible inverter, an LC filter, a converter output current and voltage sensor unit, a radio interference filter, a load current and voltage sensor unit, a load, a controlled network switch, a network current and voltage sensor unit, a network, a control unit for the DC/DC voltage converter and a voltage pulse unit, a unit control of a reversible inverter, microprocessor control and switching unit.

In addition, the device may additionally contain a battery (AB) and a bidirectional DCZDC converter

5 voltages for charging/discharging the battery, a supercapacitor block (SCB) and a bidirectional DC/DC voltage converter for charging/discharging the supercapacitor block, as well as a control unit for the battery and SCB.

The claimed solution is explained by graphic materials, where Fig. 1 shows a structural diagram of an intelligent guaranteed power supply device.

The diagram shows: solar panel unit (1), solar panel unit current and voltage sensor unit (2), DC/DC voltage converter (3), DC bus (4), current and voltage sensor unit

15 DC buses (5), reversible inverter (6), LC filter (7), current and voltage sensor unit at the converter output (8), radio interference filter (9), current and voltage sensor unit at the load (10), load (I), controlled network switch (12), current and voltage sensor unit of the network (13), network (14), DC/DC voltage converter control unit and

20 voltage pulse unit (15), reversible inverter control unit (16), microprocessor control and switching unit (17), bidirectional DC/DC voltage converter for charging/discharging the storage battery (18), storage battery (SB) (19), bidirectional DC/DC voltage converter for charging/discharging the supercapacitor unit (20), supercapacitor unit (SB) (21), voltage pulse unit (22), SB, SB control unit (23).

The device works as follows.

The voltage and current from the solar panel unit (1) through the voltage pulse unit (22) and the solar panel current and voltage sensor unit (2) is fed to the DC/DC voltage converter (3). Information about The voltage and current from the solar panels is fed to the control unit of the DC/DC voltage converter and the voltage pulse unit (15), in accordance with the specified algorithm, the unit generates control signals for the operation of the DC/DC converter and the voltage pulse unit, as a result of which the maximum possible power is taken from the solar panels at a given temperature and illumination. The received electric power is fed to the DC bus (4). From the DC bus through the DC bus current and voltage sensor unit, the voltage and current are fed to the reversible inverter (6), which in the direct conversion mode converts direct voltage and current into alternating voltage and current, for example, using pulse-width modulation. Then the power PWM signal is fed to the input of the LC filter (7), after which the filtered low-frequency signal of the network is fed to the input of the current and voltage sensor unit at the converter output (8). After which the signal is fed to the input of the radio interference filter (9). Then the output current and voltage are fed to the load (11) through the current and voltage sensor unit on the load (10), and also to the network (14) through the controlled network switch (12) and the current and voltage sensor unit of the network (13). The reversible inverter is controlled by the reversible inverter control unit (16), which receives information about the current and voltage on the DC bus, as well as at the converter output. The complete operation of the device is controlled by the microprocessor control and switching unit (17), which receives information from the DC/DC voltage converter control unit and the voltage pulse unit (15), the inverter control unit (16), from the current and voltage sensor units at the converter output, on the load and the network.

By introducing an additional voltage pulse unit between the solar panel and the DC/DC voltage converter, efficient power extraction from the solar panel unit is ensured, the energy received from the solar panel unit is increased, and flexibility and functionality are enhanced. power system of the consumer built on this converter. The voltage pulse unit (22) regularly applies voltage pulses to the SP, as if "pulls" additional electrons from the SP, which with all conventional classical methods of power extraction do not reach the conductor and recombine with holes in the SP itself. As a result, we receive more energy from the SP than with any classical methods of power extraction.

It is also possible that the system may include a storage battery (19) and a bidirectional DC/DC voltage converter unit for charging/discharging the storage battery (18).

It is also possible that the system may contain a supercapacitor unit (SCU) (21) and a bidirectional DC/DC voltage converter for charging/discharging the supercapacitor unit (20).

When introduced into the AB, BSC system, the guaranteed power supply system contains an AB, BSC control unit (23).

Due to this, an additional increase in the reliability of the guaranteed power supply of the consumer is ensured, which occurs, among other things, due to the use of energy storage devices that receive energy from solar panels and the grid according to a given algorithm, and in the event of a loss of grid voltage, a decrease in the energy received from the solar panels, they ensure uninterruptible power supply to the consumer, due to mixing energy from the storage device with the energy received from the solar panels on the common DC bus, with subsequent conversion to alternating voltage and power supply to the consumer's load.

The power supply device can act as a source of microgeneration of energy received from renewable energy sources into the network; as a source of power from renewable energy sources for the consumer's load; as a guaranteed source of power supply for the consumer in the event of a power failure from the network.

Let's consider the options for device operation in various configurations.

1. Without AB, BSK. The energy from the solar panels is taken at the point of maximum power, taking into account the reduction of parasitic recombination, and is converted into alternating voltage of the grid. Then the microcontroller analyzes the current and voltage on the load and the grid. If the energy received from the solar panels is sufficient to power the load, the converter disconnects the grid from the load and power is supplied only from the solar panels. If the load consumes less than the solar panel unit (SPU) generates, the converter directs part of the energy received from the SPU to the load and part to the grid. If the energy consumed by the load exceeds the energy generated by the SPU, the converter gives all the energy received from the SPU to the load and consumes the missing energy for the load from the grid. In the absence of a load, all the energy received from the SPU goes to the grid.

2. With AB and (or) BSC.

If the system has a battery and/or a battery-balanced synchronization unit, the general operating algorithm described above does not change, but additional operating options for the system appear. If there is energy from the battery-balanced synchronization unit and it is partially spent on the load, the remaining energy goes to charging the battery and/or battery-balanced synchronization unit. After they are fully charged, the energy goes to the grid. If the grid voltage disappears, the control and switching microcontroller disconnects the grid from the system and the load, and the consumer load is powered from the battery-balanced synchronization unit. If there is insufficient energy received from the battery-balanced synchronization unit, the stored energy from the battery and/or battery-balanced synchronization unit is supplied to the DC bus, which is then converted into alternating voltage of industrial frequency to power the consumer load. If the energy received from the battery-balanced synchronization unit is insufficient for the load and maintaining the battery and/or battery-balanced synchronization unit in a charged state for a certain period of time, then according to the specified algorithm (for example, at night), the inverter operates in the reverse mode - charging the DC bus from the industrial grid, and then the voltage converters charge the battery and battery-balanced synchronization unit to a specified level.

Let's consider the operation of a solar panel unit under various operating conditions. Fig. 2 shows a family of volt-ampere characteristics of the solar panel depending on the temperature and changes in the uniform illumination of the panel. The volt-ampere characteristic (VAC) has a classic appearance: at the initial stage, there is a linear increase in power with an increase in voltage, then an extremum is reached, after which there is a decrease in the received power with an increase in voltage on the solar panel. We see that in the VAC of the panel in this case there is only one extremum, which, with a change in temperature and a uniform change in radiation, drifts along the VAC in a limited area.

As the temperature increases, the voltage at the maximum power point decreases. The extremum of the power function on the I-V characteristic shifts down and to the left. As the temperature decreases: the voltage increases at the extremum point, the maximum power point shifts up and to the right on the I-V characteristic. As the uniform illumination of the panel decreases, the current at the maximum power point decreases, and the power extremum shifts down. As the uniform illumination of the panel increases, the current increases, therefore, the maximum power point shifts up.

There are various algorithms for tracking the maximum power point. For example, perturbation and observation or the increasing conductivity method. The essence of the perturbation and observation method is shown in Fig. 3. The voltage and current on the solar panel unit (SPU) are measured. The power P0 is calculated. Then the output voltage of the SPU is changed by controlling the converter (positive voltage increment). The current and voltage are measured. As a result, the power point P1 appears. P1 and P0 are compared, if P1 is greater, then the voltage increment remains and then the next step occurs. The voltage on the panel unit increases. The current is measured. The power P2 is calculated. Then also P3 and P4. If the new power is lower than the previous one, then the sign of the increment changes. There are also adaptive algorithms in which the increment step is not constant, but changes, depending on approaching the extremum. The step decreases in the extremum region to reduce pulsations of the power removed from the solar panel unit.

As a result, with a smooth change in temperature and a uniform change in panel illumination, the classical algorithm for finding the maximum power point tracks how the extremum drifts along the I-V characteristic of the solar panel in a given area.

In fact, all existing methods of power extraction from the solar panel are equivalent to connecting a rheostat to the solar panel and, by automatically regulating “its resistance”, provide the extraction of direct current from the solar panel at the point of the volt-ampere characteristic where the power is maximum.

The efficiency of modern industrially produced solar panels, from which energy is collected using the classical (“rheostat”) method, is in the range of 18-23%. That is, from 1 kW of solar photon energy on an equivalent rheostat load there will be 180-230 W of electricity.

The remaining energy received from solar radiation is lost in the semiconductor. The main processes leading to low efficiency of the semiconductor include: reflection of part of the radiation from the surface of the semiconductor, inactive absorption of light quanta, parasitic recombination of nonequilibrium carriers, etc.

Let us consider the operation of the SC in a simplified form, see Fig. 4. In Fig. 4: light falls on the SC and passes to the n, p regions and the depletion region. In the depletion region, the energy of the photons is transferred to the electron-hole pair. They are separated. Due to the presence of the internal field, the electrons move upward through the n region to the conductor, and then to the load. After the load, the electrons return to the SC through the conductor from the p region and recombine with the holes.

In the described manner, the energy of photons is converted into electrical energy.

However, after the separation of electrons and holes under the influence of sunlight, some of the electrons do not reach the conductor, and therefore, and loads. During the movement of electrons and holes in the depleted region, as well as partially in the n and p regions, parasitic recombination of electrons and holes occurs. As a result, most of the energy received by the SC from the sun does not reach the load due to the parasitic recombination process.

To reduce energy losses due to parasitic recombination, we will introduce a pulse voltage unit between the SC and the load. The purpose of which is to apply positive potential to the n region and negative potential to the p region of the SC by short pulses of a certain amplitude, frequency, burstiness, duration, with certain growth and decline fronts. This is done in order to give the electrons and holes that have received energy from photons an additional impulse when moving from the depleted region to the conductor. As a result of the action of these voltage pulses, the probability of parasitic recombination decreases, the number of electrons reaching the conductor and the load increases, and, consequently, the amount of energy received from the solar panel and the efficiency of the SC-converter system increase.

It should be noted that the voltage pulses have a duration of a few microseconds or less, so the energy consumption for their creation is an order of magnitude less than the energy of electrons, which do not lose it during parasitic recombination and are supplied to the load. Also, for the positive polarity of the voltage pulse applied to the n region of the SP, the p-n junction of the SP is equivalent to a closed diode.

When exposed to this "control" voltage, a large number of electrons that have received energy from light quanta that previously recombined with holes and did not reach the load, manage to exit the n layer of the SC, thereby increasing the useful energy and efficiency of the SC by 1.2-1.5 times, relative to the classical ("rheostat") methods of power extraction from the SC. To some extent, this principle figuratively corresponds to the operation of a field-effect transistor, when we use the electric field of the gate, practically without wasting current, we control the opening of the channel and the passage of power current through the p-n junctions of the field-effect transistor.

There are a large number of circuit methods for implementing the described method of increasing the efficiency of the SP-converter system. In Fig.5

5 shows one of the possible options.

Fig. 5 shows solar panel SP1, storage capacitor C1, step-up voltage converter consisting of capacitors C2, choke L1, diode D1, switch K1, pulse source consisting of transformer Tr1, capacitor C3, switch K2, power source U1 and common control device UU 1.

The control device UU1 generates control signals for the keys K1 and K2. When the key K2 briefly switches to the open state, a current pulse passes through the primary winding 1 of the transformer Tr1. A pulse is generated on the secondary winding of the transformer Tr1

15 voltage. Positive polarity applied to the n region of the solar panel SP1, and negative polarity to the p region of the solar panel SP1 through the capacitor C1. At the same time, in accordance with the specified operating algorithm, the switch K1 is periodically opened, resulting in the formation of voltage on the capacitor C2. The voltage on

20 capacitor C2 then goes either to the load or to the voltage inverter.

Light falling on solar panel SP1 separates electrons and holes. Electrons move along the circuit and charge capacitor C1. At the same time, positive voltage pulses with a given frequency, duration, amplitude, growth and decay fronts are applied to the n region of the solar panel through pulse transformer Tr1; as a result, the probability of parasitic recombination of electrons and holes decreases, and an additional number of electrons, having received energy from photons of light, reach the conductor and charge the storage capacitor C1. Then, through the step-up converter (LI, KI, DI, C2), the voltage increases to the level required for the load or for the inverter voltage.

Transformer Tr1 can be made either with or without a ferromagnetic core.

Fig. 6 shows a diagram of a possible series (a) and parallel (b) connection of solar panels using an example of two panels. When connecting the solar panels in blocks, diodes are connected in parallel to the solar panels, which serve to bypass the current during partial shading of the solar panels in the panel block. In order for these diodes not to shunt the pulse signals that are applied to the solar panels, chokes (L2-L4) are installed in series with each of the diodes (D2-D4). These chokes have virtually no resistance to direct current, and during partial shading, direct current passes through the diodes. At the same time, when exposed to voltage pulses from transformer Tr1 (Fig. 5) with a duration of a few microseconds or less, chokes D2-D4 have a high wave resistance and do not shunt these pulses.

The claimed solution allows to increase the amount of energy received from the solar panel array under real operating conditions. This is of primary importance both for autonomous power supply systems without a network and for systems with a network, since it ultimately affects the amount of energy received from solar panels.

Claims

Formula

1. A power supply device based on solar batteries consisting of a solar panel unit, a solar panel unit current and voltage sensor unit, a DC/DC voltage converter, a DC bus, an inverter, a unit of current and voltage sensors at the converter output, a DC/DC voltage converter control unit, an inverter control unit, a control and switching microcontroller, a unit of DC bus current and voltage sensors, an LC filter and a radio interference filter, a unit of current and voltage sensors on the load, connected to each other, characterized in that a voltage pulse unit installed between the solar panel and the DC/DC voltage converter is additionally introduced into it.

2. A power supply device according to item 1, characterized in that the DC/DC voltage converter control unit is designed with an additional function for controlling the voltage pulse unit.